SV-POW! … All sauropod vertebrae, except when we're talking about Open Access

How big was Futalognkosaurus?

January 16, 2008

Futalognkosaurusdukei, just described last year, may be the most complete giant dinosaur ever discovered. Maybe. Depends on what you compare it to, and it also depends on how it’s measured. It’s hard to say right now because only one short paper on it has been published to date (Calvo et al. 2007), and it only includes one figure of the beast. Let’s take a look.

Figure 2 from Calvo et al. (2007)

Now, according to the skeletal reconstruction and the 2 meter scale bar, the total length of the cervical series is 10.6 meters, the dorsal column is 4.85 meters long, and the sacrum is 1.75 meters long. By way of comparison, the complete cervical series of the HM SII skeleton of Brachiosaurus brancai is 8.5 meters (or would be, with the two missing cervicals included), and the really complete, articulated neck of Mamenchisaurus hochuanensis is 9.5 meters. So Futalognkosaurus indeed looks like a whopper.

But hang on a second. The figure also includes scale photos of several of the elements. It’s a cinch to use those scale bars to figure the size of the photographed elements, and compare the measurements obtained that way to the size of the same elements in the skeletal reconstruction. I made all the measurements using the ruler tool in Photoshop, and here’s what I got (feel free to do your own and compare). In each line, the first number is the one I get from the scaled skeletal reconstruction, the second is the number I get from the scaled photograph, and in parentheses is the second as a percentage of the first.

C2 is 18 cm… or 29 cm (161%)

C6 is 79 cm… or 46 cm (58%)

C10 is 94 cm… or 89 cm (95%)

C14 is 94 cm… or 50 cm (53%)

Caudal 1 is 92 cm tall… or 72 cm tall (78%)

Pubis is 149 cm … or 141 cm (95%)

Now, it’s interesting that except for C2, which is small and hard to draw right (trust me), all of the measurements based on photos are smaller than the measurements based on the skeletal reconstruction.

The only measurement given in the paper–other the total length of the animal, estimated at 32-34 meters (105-111 feet)–is the length of the pubis, which is actually 137 cm, which is 97% of the size indicated by the scaled photo and 92% of the size indicated by the skeletal reconstruction.

The story gets more interesting. As you can see from the numbers I slapped on the illustration, the reconstruction includes 14 cervicals, 11 dorsals, 6 sacrals, and 1 caudal. But in the character matrix at the end of the paper, Futalognkosaurus is coded as having 14 cervicals, 10 dorsals, and 6 sacrals. So either the skeletal reconstruction has an extra vertebra, or the dorsal count is miscoded.

If the skeletal reconstruction is accurate (and everything else wrong), the total length of the neck, trunk, and sacrum is 17 meters, so a total length of 30+ meters is pretty reasonable. But if everything else is right, the skeletal reconstruction is too big, by anywhere from 5-47%. I don’t think it’s really half again too big, but I’ll bet that the real number is lurking in there somewhere, probably around 15%.

So what’s the point? Why did I write the post?

Well, I certainly didn’t do it to make Calvo et al. look careless or stupid. The fact is, it is really, really easy to get scale bars wrong, and really, really hard to get skeletal reconstructions right. I have screwed up both (see Wedel 2000 for evidence). Big things are hard to measure, and it is perilously easy to get the numbers wrong. In the original paper on Sauroposeidon I (my coauthors are blameless here) wrote that it had 12-meter neck, the longest of any known animal. Turns out neither of those things is true. The most liberal neck estimate for Sauroposeidon is 11.5 meters, and the most conservative is only 10.5 meters. And Supersaurus had a longer neck, at least 13 or 14 meters no matter how you get there (Wedel and Cifelli 2005).

Here’s another example. Crack open just about any dinosaur book and you’ll read that Mamenchisaurus had a neck 33 feet long. But it ain’t the case. Tote up the lengths of the individual vertebrae in Young and Zhao (1972) and you’ll get 31.5 feet (9.5 meters). Stretch a tape measure along the mounted skeleton and you’ll get the same result. So where did the number 33 come from? Beats me. But a lot of people have repeated it, when the real numbers are not hard to get (at least for the people doing the repeating).

Also, I can’t fault Calvo et al. for publishing a short description of Futalognkosaurus, as long as they follow up with something more substantial later. It’s pretty common in biology (not just paleo), and it’s exactly what Rich and Kent and I did with Sauroposeidon. Describing things is a time-consuming process–four measly vertebrae were enough to keep me busy for years–and there are lots of reasons why it may be good to get something out now and follow up with the monograph as time and circumstances allow (but do follow up).

I wrote the post for the same reason I do all this stuff–when it comes to sauropods and their vertebrae, my curiosity knows no bounds. As soon as I saw the Futalognkosaurus description I knew I’d eventually dig in and see how big the critter is supposed to be. And now I have an outlet for that kind of nerdosity, hence the post.

The moral of the post, if there is one, is that tables of measurements are usually harder to screw up than scaled figures (but by no means invulnerable to error). And that until a more complete description of Futalognkosaurus appears–hopefully with a table of measurements–it’s hard to say how big it was. Maybe it was bigger than Brachiosaurus. Maybe not.

Like this:

Related

40 Responses to “How big was Futalognkosaurus?”

Comparing Futalognkosaurus with Brachiosaurus brancai, the one measurement we have to go on right now is that of the pubis. As you pointed out, it’s 137 cm long in Futalognkosaurus (Calvo et al. 2007:532). Janensch’s (1961) monograph of the appendicular skeletons of Tendaguru sauropods gives the measurements of four B. brancai pubes: 74, 83, 89 and 121 cm for the specimens T28, R21, J2 and SII respectively (Janensch 1961:201). But we also know that the B. brancai fibula XV2 is 134 cm long compared to 119 cm for that of SII (Paul 1988:3), so it was presumably from an animal about 134/119 = 1.126 times as big in linear dimension. That suggests its pubis was 1.126*121 = 136 cm long … one cm shorter than that of Futalognkosaurus.

So — not that I advocate extrapolating whole-animal sizes from pubis length, you understand — it does seem that, based on this since actual measurement, Futalognkosaurus is almost exactly comparable to the largest known Brachiosaurus brancai individual.

So — not that I advocate extrapolating whole-animal sizes from pubis length, you understand — it does seem that, based on this since actual measurement, Futalognkosaurus is almost exactly comparable to the largest known Brachiosaurus brancai individual.

Surely: potentially yes, ifFutalognkosaurus was a brachiosaur. But it’s a titanosaur, and their proportions are different from those of brachiosaurs. They have a proportionally longer tail and perhaps a longer body too. In other words, if a big titanosaur had a pubis comparable in size to that of a big brachiosaur, I’d expect the titanosaur to be longer.

In the HM SII specimen of Brachiosaurus, the pubis is about 60% of the length of the femur. In Rapetosaurus and Opisthocoelicaudia, the pubis is 80-85% of the length of the femur. There are no femora for Futalognkosaurus right now, but if it was built like other titanosaurs its femur might have been only 1.6-1.7 meters long–30 or 40 cm shorter than that of HM SII. And titanosaur humeri are a bit shorter than the femora, so the humerus of F. dukei might have been 1.5 meters long, or even less–not small, but smaller than the humeri of Turiasaurus and Paralititan and some others. So it’s really not clear at all that F. dukei is the most complete giant dinosaur ever found.

Like I said in the article, it all depends on how it’s measured. The dorsal series of HM SII was probably 3.8 meters long (filling in the missing bits). The naive reading of the F. dukei skeletal reconstruction gives it a dorsal series a full meter longer. But given the apparent problems with the reconstruction, including scaling issues and the possible extra vert, it is entirely possible that the dorsal series of F. dukei was no longer than that of HM SII. So the pubis (and other pelvic elements) might be the only part of Futalognkosaurus that was bigger than its counterpart in HM SII, let alone XV2.

I see this sort of stuff all the time. I just can’t trust any images unless a good quality photograph with a ‘physical’ scale bar (as in a photographed one) is present.

As for mamenchisaurus I’ve heard has high as 15m in many books. Mr Wedel, you say in Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon” that M. Sinocanadorum has a 4.1m long cervical rib. In the M. Hochuanensis paper they say the longest is only 2.1m about half the length of M. Sinocanadorum. I have a suspicion that this is where the large neck lengths for mamenchisaurus are coming from. Does anyone know how long the cervical vertebra in M. Sinocanadorum are?

Hi, Steve, good to hear from you. As you no doubt know, Mamenchisaurus sinocanadorum is a different species from M. hochuanensis. Unlike the latter, it is known from very incomplete remains: there is some OK cranial material, but beyond that only the first three cervicals were found an prepared, so most of what can be said about it is only guesswork. That said, the preserved elements are indeed larger than their counterparts in M. hoch. Russell and Zheng’s (1993) description of the new species points out (p. 2091) that the preserved cervicals are on average 1.19 times as long as those of M. hoch, which suggests a total neck length of 9.5 x 1.19 = 11.3 m. I can’t see any justification at all for 15 m.

(By the way, Russell and Zheng 1993 has the distinction of being, AFAIK, the earliest paper to include a cladistic analysis of sauropods: 21 characters, 9 taxa. Interestingly, it recovered Euhelopus as part of what we’d now recognise as the Macronarian clade, along with Brachiosaurus and Camarasaurus … although most of the rest of its results were badly wrong judged by recent analyses.)

I suspect that the longest cervical ribs of M. hochuanensis were longer than 2.1 meters. Very long cervical ribs tend to taper down to almost nothing. The cervical ribs of Sauroposeidon get down to pencil lead size before they peter out. It takes really great preservation and really careful preparation to get those skinny ends. I have seen the 4.1-meter rib of M. sinocanadorum in the flesh, and it is in spectacular shape.

Anyway, only the first few cervicals of M. sinocanadorum are preserved. On average, they are about 25% longer than those of M. hochuanensis, which indicates a neck 12 meters long. There is also a news report from China (sadly, no paper yet) on a new specimen of Mamenchisaurus with a 12-meter neck. From my back-of-the-envelope calculations, the giant mamenchisaur mentioned at SVP last year would also have been in that league. I don’t know of any fossils that might represent mamenchisaurs with necks longer than 12m, but that doesn’t mean we won’t find any.

As I was typing this I got a message that Mike had left a comment on this post, and see that he has said some of the same stuff. Man, are we a responsive bunch or what?

That’s been bugging me for years and what’s odd is that you hear really specific measurements, one book in particular as specific as 14.9 m. I wonder where on earth (or the universe) they get them from.

This blog is awesome, and thanks to you guys for making dinosaurs seem so interesting (it actually is anyway). I’m just a general fan and don’t have the specific knowledge on actual bone lengths/details, so I can’t go into discussion about that. However, what weapons did the large sauropods have to defend against potential predators apart from their size? For example, elephants have tusks, rhinos have their horn.

Well done, gents. Moral of the story seems to be this: Scale bars are tough to get right, and maybe this beastie wasn’t quite as big as the picture makes it out to be. Still an incredible animal. Now, I was under the impression that Supersaurus was not a valid taxon?

When I say book, please don’t think any mayor scientific book or journal like Thunder Lizards or PDTW.
………OK, Before I lose any credibility I don’t take the book seriously. I have had it for years. It was published before 1993……

The book that says 14.9m is the Eyewitness Visual Dictionary of Dinosaurs reprinted in 1993 by DK……….. It probably doesn’t exist anymore.
It’s not just that book I’ve heard it. I’ve heard similar measurements in many other places over the years. And because they’re often such specific measurements they must get it from somewhere?? Even if it’s based on an out of date estimate, I doubt the figure was made up.
Looking on google books The Kingfisher Illustrated Dinosaur Encyclopedia By David Burnie states 14 m. Again, obviously it’s not a primary source……I’ve been having a quick look around the internet at books. It’s usually small books like these. Maybe they’re not checking their figures or getting them from other similar books rather than scientific sources.

Richard: Glad you like the blog. As for sauropod weapons…I’m not sure of the official standing of the whip-tail defense right now, but I can tell you that iguanas can hit hard enough with their tails to draw blood. So I wouldn’t rule it out. And at least some of the Chinese sauropods had little clubs on the ends of their tails. Finally, sheer size is often overrated underrated. Big things can hit hard (spend some time around cattle and you’ll find out what I mean). According to the Audubon Encylopdeia of Animal Life that I got when I was 12, there is a case of a lion getting its head knocked completely off by a single kick from a giraffe. Sure, theropods were faster and smarter than sauropods. But when a single thump from a tail or limb could result in a broken leg and slow death, they were probably very careful about who they picked on, and when–just like modern predators.

Zach: We get this one a lot. :-) The short version is, Ultrasaurus is non-diagnostic crap from Korea, Ultrasauros is sunk, but Supersaurus has never stopped being a valid taxon since it was named in 1985. And it’s looking better than ever these days, with a new and more complete specimen from Wyoming about to be described. There is a short, accurate summary of the whole affair here.

Steve O’C: No need to be sheepish. Now that you mention it, I recall seeing the same stat in the same book. I don’t know where they get stuff. I have seen some pretty funny screwups in which names and stats from Mamenchisaurus, Sauroposeidon, and/or Supersaurus were combined, especially the strange case of Superposeidon.

Regarding inaccurate but over-precise measurements in books: I bet these mostly come from unit convesion. In a bar after a conference, someone asks Dale Russell how long the neck of M. sinocanadorum was. Has says “Maybe as much as fifty feet in a really big specimen”. That becomes “the neck of M. sinocanadorum was 15·24 m in length”.

I thought that could be a likely possibility. I have been looking around the net, and found something interesting, a ‘mamenchisaur’ called Hudiesaurus sinojapanorum. Maybe early rumours of this animal before it was described are responsible? You could imagine someone asking ‘how big’ and getting a reply ‘there’s an un-described mamenchisaur specimen that’s massive, maybe with a 50 ft neck’. That becomes MamenchisaurUS with a massive neck.

That is pretty much de rigeur in newpapers here where we get a lot of stuff from US sources and the idiot editors convert measures to metric with improbable precision. Still, it’s not as bad as being told to convert length of ships (some of them Great Lakes ore carriers) in feet to the nearest millimetre, as I was in a summer job for the Coast Guard.

[…] to the two recons, those sources of data do not agree (hmm…where have we seen this problem before?). Also, the whole skeleton of Isisaurus is not known so a lot of what you see here is guesswork. […]

So then, does F.Dukei push argentinosaurus and Puertasaurus and that kind of thing right out of the spotlight?
anyway, could you tell me how big these sauropods were?=
Borealosaurus
Gobititan
Muyelensaurus
Mendozasaurus

I’d furthermore like to know about ruyangosaurus and huanghetitan ruyangensis 9like their length and where exactly in titanosauria they fit. It’d be nice if oyu could tell me when the others above lived as well (what stages in the cretaceous)

Isn’t brachiosaurus altithorax bigger than brachiosaurus brancai? altithorax being 14m tall & 26m long and brancai being 12m tall & 22.5m long.If so why is brancai being used as a comparison when it was a small brachiosaurus?

Your right some dinosaur publications do exaggerate the sizes of the dinosaurs, i have seen Brachiosaurus quoted with a height of 15m and Mamenchisaurus with an 11m neck many times. But recently i found out that a Mamenchisaurs cast had been made in china measuring 35m, i mean has a new discovery been made? I always assumed Mamenchisaurus grew to about 22m-23m.

“Brachiosaurus” brancai (i.e. Giraffatitan) is always used as the standard of comparison rather then the type species Brachiosaurus altithorax, because it is represented by much better fossils — basically the whole skeleton, whereas we have maybe a quarter of Brachiosaurus proper. Height and length estimates for Brachiosaurus are extremely sketchy given the paucity of material. For details, see “Taylor (2009) on Brachiosaurus” over in the sidebar.

Lots of “casts” get made for nearly wholly imaginary skeleton, such as the Fernbank Museum’s alleged Argentinosarus skeleton. So I wouldn’t put too much store in that 35 m mamenchisaur. That said, there is good evidence for a mamenchisaur (M. sinocanadorum) with a 12 m neck, based on cross-scaling the few cervical vertebrae that are known with those of better-known species.

So how long would a 12m long neck mamenchisaurus be? Just shows that the first skeleton of a new dino found is usually dwarfed by later discovery. There must be a larger argentinosaurus and supersaurus etc out there!

Have you read that the 33 meter 70 tonnes Futalognkosaurus, ”the most complete giant sauropode known so far”, has been shrunk in a 26 meter 25 tonnes animal?
How it is possible such a big discrepancy with respect to the initial estimations?
And Futalognkosaurus is pretty much complete.. At this point I think many of the purpoted giants could be totally off as well

[…] had a very clear idea of the proportions of the largest titanosaurs (sometimes because of conflicting measurements). So now we can start investigating questions involving the biomechanics and hopefully the growth […]

[…] et al. for the rare feat of having everything pretty much to scale, and a properly-sized scale bar. This is not always the case. Presumably having a 3D digital model of the reconstructed skeleton helped — and BTW, if you […]